1) Field of the Invention
This invention relates to sealant compositions, particularly for sealing joints. It is particularly concerned with anaerobic sealant compositions used in sealing joints in pipework and other fluid conduits, particularly joints between interfitting male and female co-axial components, especially threaded components.
2) Description of the Prior Art
Plumbers currently use a variety of sealants for sealing joints in pipework. The traditional form of sealant is a combination of a hemp cord (which is laid in the helical thread of one component) and a linseed oil formulation known as "bosswhite." This involves an undesirable amount of manual labour. Anaerobic acrylic resin compositions, which cure spontaneously when oxygen is excluded as a result of assemble of interfitting components, are commercially available as pipe sealants, but they are sometimes criticised on the ground that the composition does not provide a leak-proof seal in a short enough time. Plumbers wish to be able to test a joint in pipework under pressure immediately after interfitting of the components.
Modification of the sealant composition to reduce the cure time is generally not acceptable because a plumber needs to be able to adjust the relative angular position of two components by as much as 45.degree. for some time, at least 24 hours after assembly of the components without breaking the seal. It is desirable therefore that the sealant composition should seal the joint almost immediately but should not lock the joint, at least for 24 hours.
Particulate fillers have been added to such compositions but they tend to increase the viscosity of the composition to the extent that it is difficult to apply.
Aramid fibre pulp, such as that sold under the Trademark KEVLAR by E. I. Du Pont de Nemours & Co., has been described as thixotrope for sealants, adhesives and coatings (Frances et al, Adhesives Age, April 1988, 27-30) Frances et al of E. I. Du Pont de Nemours & Co. tested aramid fibre pulp in a number of adhesives and sealants including epoxy, neoprene, PVC, plastisol, asphalt, polybutadiene, polyurethane and silicone American Fillers & Abrasives Inc. of 14 Industrial Park Drive, Bangor, Mich. 49013, U.S.A. offers KEVLAR pulps for use in adhesives, sealants, coatings, etc. to give thixotropic properties at low addition levels (Adhesives & Sealants Newsletter, Mar. 14, 1988). However there is no teaching concerning the use of aramid fibre pulp in an anaerobic acrylate polymer composition, or of the effect of such pulp in achieving a rapid seal with an anaerobic joint sealing composition.